Surface plasmon polaritons excited by electromagnetic waves

We investigate surface plasmon polaritons (SPPs) excited by electromagnetic waves at an interface of two media. In sharp contrast to the current understanding of SPPs, we found that when the excitation field is present, the tangential components of the electrical field and the magnetic field at the boundary cannot be simultaneously continuous for SPPs. Surface current and/or charge densities will have to be non-zero to maintain the self-consistency of the Maxwell's equations. In addition, SPPs can exist for both polarizations and are intimately related to the well-known skin effect of the AC current in metal conductors. We present the results of general conditions for SPP excitation, the non-zero surface source distributions, and the skin depth of the SPPs.